Maryl-Axd Geologic \l Survey 607 



Dcscriplion. — '' Slicll of medium size, sub-ovate, widest at the posterior 

 end; length more than one-third greater than the height; liasal margin 

 regularly convex, sometimes straight, or constricted toward the anterior 

 end. Posterior extremity rounded, or obtusely subangular, often sub- 

 truncate above. Cardinal line nearly straight. Anterior end short, ab- 

 ruptly rounded below the lunule. Valves moderately convex in the lower 

 and posterior part, becoming gibbous in the middle and umbonal region. 

 Beaks subanterior, prominent, inclining foi'ward and strongly incurved. 

 Umbonal slope rounded. Postcardinal slope flattened or concave, some- 

 times limited by an elevation, at which line the concentric undulations 

 terminate. Anterior to the middle of the shell, extending from the l)eak 

 to the basal margin, there is a depression or cincture which often gives a 

 slight undulation to the concentric folds and a constriction to the margin. 

 Surface marked by fine, close concentric strife and by strong subangular 

 concentric ridges or folds, which are frequently duplicate posterior to the 

 cincture. The surface is also marked by fine, radiating pustulose striae, 

 which are often very conspicuous. Interior unknown. Three specimens 

 measure respectively 36, 38, and 48 mm. in length, 9,nd 20, 23, and 33 

 mm. in height. The largest specimen observed has a length of 70 mm. 

 This species resembles G. arcxiata in its general aspect, but differ? in its 

 more elongate form, more pointed posterior end, and the cincture is much 

 more strongly marked." Hall, 1885. 



Occurrence. — Jennings Formation, Chemung Member. National 

 Eoad, on Polish Mountain, 2503. Parkhead Member. Allegany Grove, 

 950; Williams Eoad, on Polish Mountain, 1289. 



Collection. — Maryland Geological Survey. 



Grammysia communis Hall 

 Plate LIX, Figs. 14, 15 



Grammysia communis Hall, 1885, Pal. of N. Y., vol. v, pt. 1, ii, p. 378, pi. 



ixi, figs. 24-28; pi. xciii, fig. 20. 

 Grammysia communis Grabau and Shimer, 1909, N. Araer. Index Foss., vol. 



1, p. 383, fig. 27. 



Description. — '"'Shell small, ovate-cuneate; length less than twice the 

 height ; basal margin gently curving with a slight constriction just ante- 



